Added GoogleDisplayVideo360DownloadLineItemsOperator

[michalslowikowski00]

Added new operator for Display Video service.

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• Description above provides context of the change
• Unit tests coverage for changes (not needed for documentation changes)
• Commits follow "How to write a good git commit message"
• Relevant documentation is updated including usage instructions.
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[codecov-io]

Codecov Report

Merging #8174 into master will decrease coverage by 27.73%.
The diff coverage is 54.05%.

@@             Coverage Diff             @@
##           master    #8174       +/-   ##
===========================================
- Coverage   88.45%   60.72%   -27.74%     
===========================================
  Files         937      937               
  Lines       45234    45260       +26     
===========================================
- Hits        40011    27483    -12528     
- Misses       5223    17777    +12554     

Impacted Files	Coverage Δ
...s/google/marketing_platform/hooks/display_video.py	44.11% <33.33%> (-55.89%)	⬇️
...ogle/marketing_platform/operators/display_video.py	61.22% <50.00%> (-34.06%)	⬇️
...ing_platform/example_dags/example_display_video.py	100.00% <100.00%> (ø)
airflow/providers/exasol/operators/exasol.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/amazon/aws/hooks/kinesis.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/apache/livy/sensors/livy.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/amazon/aws/sensors/redshift.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/mysql/operators/s3_to_mysql.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/postgres/operators/postgres.py	0.00% <0.00%> (-100.00%)	⬇️
airflow/providers/microsoft/azure/operators/adx.py	0.00% <0.00%> (-100.00%)	⬇️
... and 324 more

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[turbaszek]

Build were canceled but test seems to be ok